"What's going to be happening for the next probably 10 days there are going to be intrusion of smoke from these wildfires," said Sally Markos with the Lane Regional Air Protection Agency. "Until we get a major storm systems coming through or they get the fires under control, this is going to repeat."

Markos said she has fielded reports Tuesday morning of smoke and ash in south Eugene along Willamette Street; in Lowell, Ore.; and in downtown Eugene.

"As long as we have really low humidities and the wind speed picks up, that fire is going to get larger and we are going to get smoke in the valley," Markos said.

On Monday night, Markos saw a ribbon of smoke stretch north along the Coburg Hills towards Junction City and southwest all the way to the Coast. Markos said a weather forecast she reviewed this morning had satellite imagery that showed smoke all the way to the coast.

Markos said winds carried the smoke and ash aloft in the upper atmosphere. Cold air inversions overnight can bring what is in the upper atmosphere down to ground level, Markos said.

Also, when the wind is from the east, air can flow down from the Cascades like a river, carrying with it whatever is in the air -- like smoke and ash.

When the sun comes up and starts warming the air, the air mixes and the smoke in the air dilutes.

Markos said anyone with respiratory problems should be cautious when exercising when the smoke is in the air.